Polyester polymers comprising lignin

ABSTRACT

Disclosed is a polyester polymer prepared from a reaction mixture comprising a polyacid component and a polyol component that comprises lignin. Residues of lignin are incorporated into the backbone of the polyester polymer. Coatings comprising the same and substrates coated at least in part with such coatings are also disclosed.

FIELD OF THE INVENTION

The present invention relates to polyester polymers prepared from ligninsuch that the lignin is incorporated into the backbone of the polyesterpolymer. The present invention further relates to coatings comprisingsuch polyester polymers and substrates to which such coatings areapplied.

BACKGROUND OF THE INVENTION

Polyester resins are used in coating compositions either as a primary oradditive resin and may be crosslinked using a crosslinking agent to forma film of coating composition on a substrate upon application andcuring. Certain components of a polyester resin are costly, yet aretraditionally considered necessary in order to provide a particularcombination of characteristics such as smoothness, gloss, andperformance characteristics such as chemical resistance, mar resistanceand resistance to weathering or the like.

SUMMARY OF THE INVENTION

The present invention includes a thermoset coating compositioncomprising a polyester polymer prepared from a reaction mixturecomprising (a) a polycarboxylic acid component and (b) a polyolcomponent comprising lignin, such that residues of lignin areincorporated into the polyester.

Coatings include clearcoats and primer compositions comprising suchpolyester polymers are also within the scope of the present invention asare substrates coated at least in part with such coatings.

DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. Further, in this application, the use of “a”or “an” means “at least one” unless specifically stated otherwise. Forexample, “an” aromatic monoacid, “a” polyacid, “a” polyol, “an”aliphatic polyacid, and the like refers to one or more of any of theseitems.

As used herein, the transitional term “comprising” (and other comparableterms, e.g., “containing,” and “including”) is “open-ended” and is usedin reference to compositions, methods, and respective component(s)thereof, that are essential to the invention, yet open to the inclusionof unspecified matter. The term “consisting essentially of” refers tothose component(s) required for a given embodiment and permits thepresence of component(s) that do not materially affect the properties orfunctional characteristic(s) of that embodiment. The term “consistingof” refers to compositions and methods that are exclusive of any othercomponent not recited in that description of the embodiment.

The present invention is directed to polyester polymers that may be usedto form coatings included, but not limited to, clear coatings and primercoatings that can be applied to at least a portion of a substrate. Asused herein, the term “polymer” refers to oligomers and bothhomopolymers and copolymers. The term “resin” is used interchangeablywith “polymer.” The polyester polymer of the present invention comprisesa polymer prepared from a reaction mixture comprising a polyacidcomponent and a polyol component comprising lignin. Upon reaction,residues of the lignin are incorporated into a backbone of the polyesterpolymer. The polyester polymer may be dissolved or dispersed in asolvent. Coatings, which may be clear or tinted, comprising suchpolyester polymers incorporating lignin, are also within the scope ofthe present invention, as are substrates coated at least in part withsuch coatings, with or without an underlying base coat.

The term “polyacid” is used herein to refer to a compound having two ormore acid groups and includes the ester and or anhydride of the acid. Inone embodiment of the invention, the acid comprises a branched acid suchas isophthalic acid, including its ester and/or anhydride. In certainother embodiments, one or more additional acids, including monoacids,can also be used. “Monoacid” and like terms, as used herein, refers to acompound having one acid group and includes the ester and/or anhydrideof the acid. It will be understood by those skilled in the art that apolycarboxylic acid is one that has two or more carboxylic acidfunctional groups, or residues thereof, such as anhydride groups.Suitable polyacids include but are not limited to saturated polyacidssuch as adipic acid, azelaic acid, sebacic acid, succinic acid, glutaricacid, decanoic diacid, dodecanoic diacid, cyclohexanedioic acid,hydrogenated C36 dimer fatty acids, and esters and anhydrides thereof.Suitable mono acids include but are not limited to cycloaliphaticcarboxylic acids including cyclohexane carboxylic acid, tricyclodecanecarboxylic acid, camphoric acid, and aromatic mono carboxylic acidsincluding benzoic acid and t-butylbenzoic acid; C1-C18 aliphaticcarboxylic acids such as acetic acid, propanoic acid, butanoic acid,hexanoic acid, oleic acid, linoleic acid, nonanoic acid, undecanoicacid, lauric acid, isononanoic acid, other fatty acids, and thosederived from hydrogenated fatty acids of naturally occurring oils suchas coconut oil fatty acid; and/or esters and/or anhydrides of any ofthese. The additional acids comprise, at most, less than 10 mole %, suchas no more than 5 mole % of the total acid and polyacids used in formingthe branched polyester polymer.

In certain other embodiments, the additional monoacid comprises benzoicacid, its ester and/or its anhydride. In certain of these embodiments,the benzoic acid, its ester and/or its anhydride comprises up to 25weight % of the total weight of the branched polyester polymer. Incertain of these embodiments, the benzoic acid, its ester and/or itsanhydride comprises between 5 and 15 weight % of the total weight of thebranched polyester polymer. In certain of these embodiments, the benzoicacid, its ester and/or its anhydride comprises between 10 and 15 weight% of the total weight of the branched polyester polymer, such as 15weight percent.

As noted above, the polyester polymer is prepared from a polyolcomponent that comprises lignin. The polyol component may also includeother polyols in addition to lignin. Lignin includes hydroxyl functionalresidues such that lignin functions as a polyol in the reaction of apolyol with a carboxylic acid to produce polyester.

Lignin is a macromolecular compound having a reactivity that can bedetermined by its particular structure with certain functional groups,which may include hydroxylic groups, both phenolic and aliphatic. Ligninhas a heterogeneous structure and typically lacks a defined primarystructure. In one embodiment, the lignin comprises wheat straw lignin, alignin that is isolated from wheat straw. Alternatively, the lignin maycomprise wood lignin, also referred to as organosol lignin, referring tothe technique for separating wood lignin from cellulose materials viaextraction with multiple organic solvents. As used herein, “organosollignin” refers to such wood lignin. While lignin has been utilized asfiller material in coating compositions, the present inventionincorporates the lignin directly into the polymeric backbone of thepolyester polymer. In certain embodiments, coating compositions of thepresent invention include lignin as a filler (e.g., in powder form) aswell as incorporating lignin in the polymer backbone.

In embodiments where the polyester polymer is prepared from a reactionmixture that contains lignin as well as other hydroxyl functionalcomponents (e.g., polyols) the weight ratio of lignin to the hydroxylfunctional components may range from 1:30 to 30:1, and the lignin maycomprise 1-50 weight % of the polyester polymer, with the weight percentbased on total solids of the end product.

In certain embodiments, the polyester polymer of the present inventionis dissolved or dispersed in a solvent or a mixture of solvents.Typically, solvents that can be used to dissolve or disperse thepolyester include, but are not limited to, water, organic compounds, andmixtures thereof. In certain embodiments, the solvent may besubstantially free, may be essentially free, or may be completely freeof water. The term “substantially free of water” means that the solventcontains less than 1000 parts per million (ppm) of water, “essentiallyfree of water” means that the solvent contains less than 100 ppm ofwater, and “completely free of water” means that the solvent containsless than 20 parts per billion (ppb) of water.

Non-limiting examples of organic solvents that can be used to dissolveor disperse the polyester include glycols, glycol ether alcohols,alcohols, and ketones. Other non-limiting examples of organic solventsinclude aromatic hydrocarbons, such as xylene and toluene and thoseavailable from Exxon-Mobil Chemical Company under the SOLVESSO® tradename; acetates including glycol ether acetates, ethyl acetate, n-butylacetate, n-hexyl acetate, and mixtures thereof; mineral spirits,naphthas and/or mixtures thereof. “Acetates” include the glycol etheracetates.

In certain embodiments, the amount of solvent added to disperse ordissolve the polyester is such that the polyester is 30 to 95 weight %based on resin solids. In certain embodiments, the amount of solventadded to disperse or dissolve the branched polyester is such that thepolyester is 60 to 95 weight %, such as 85 weight %, based on resinsolids. As a result, polyesters with extremely low volatile organiccompounds (VOCs) may be obtained.

As mentioned above, the present invention is also directed to coatingcompositions that include any of the polyesters described above and acrosslinker. The crosslinker may be chosen to be reactive with thefunctional group or groups on the polyester. It will be appreciated thatthe coatings of the present invention can cure through the reaction ofthe hydroxyl groups and/or other functionality in the polyester and thecrosslinker.

Non-limiting examples of crosslinkers include phenolic resins, aminoresins, epoxy resins, beta-hydroxy(alkyl) amide resins, alkylatedcarbamate resins, isocyanates, polyacids, anhydrides, organometallicacid-functional materials, polyamines, polyamides, aminoplasts, andmixtures thereof.

Non-limiting examples of isocyanates include multifunctionalisocyanates. Examples of multifunctional polyisocyanates includealiphatic diisocyanates, such as hexamethylene diisocyanate andisophorone diisocyanate, and aromatic diisocyanates such as toluenediisocyanate and 4,4′-diphenylmethane diisocyanate. The polyisocyanatescan be blocked or unblocked. Examples of other suitable polyisocyanatesinclude isocyanurate trimers, allophanates, and uretdiones ofdiisocyanates, and polycarbodiimides, such as those disclosed in U.S.Pat. No. 8,389,113, incorporated by reference in pertinent part herein.Suitable polyisocyanates are well known in the art and widely availablecommercially. Examples of commercially available isocyanates includeDESMODUR® N 3300A, DESMODUR® Z 4470RA, DESMODUR® N 3900, and DESMODUR® N3400, which are commercially available from Bayer Corporation.

Non-limiting examples of aminoplasts include condensates of aminesand/or amides with aldehyde. The most common amines or amides aremelamine, urea, or benzoguanamine. For example, the condensate ofmelamine with formaldehyde is a suitable aminoplast. However,condensates with other amines or amides can be used; for example,aldehyde condensates of glycoluril. While the aldehyde used is mostoften formaldehyde, other aldehydes, such as acetaldehyde,crotonaldehyde, and benzaldehyde may be used.

The aminoplast contains methylol groups and at least a portion of thesegroups may be etherified with an alcohol to modify the cure response.Any monohydric alcohol may be employed for this purpose includingmethanol, ethanol, butanol, and hexanol. Suitable aminoplasts resins,such as CYMEL® 202 or CYMEL® 303, are acceptable examples acting ascuratives and are available from Cytec Industries.

In certain embodiments, to prepare coatings using the polyesters andcrosslinkers described above, the polyesters and crosslinkers can bedissolved or dispersed in a solvent or a mixture of solvents. In certainembodiments, the solvent may be substantially free, may be essentiallyfree, or may be completely free of water. The term “substantially freeof water” means that the solvent contains less than 1000 parts permillion (ppm) of water, “essentially free of water” means that thesolvent contains less than 100 ppm of water, and “completely free ofwater” means that the solvent contains less than 20 parts per billion(ppb) of water.

Non-limiting examples of solvents that can be used to dissolve ordisperse the polyesters and crosslinkers include any of the solventsdescribed above. For instance, in certain embodiments, the solvent is anorganic solvent that can include, but is not limited to, glycols, glycolether alcohols, alcohols, and ketones; aromatic hydrocarbons, such asxylene and toluene and those available from Exxon-Mobil Chemical Companyunder the SOLVESSO® trade name; acetates including glycol etheracetates, ethyl acetate, n-butyl acetate, n-hexyl acetate, and mixturesthereof; and mineral spirits, naphthas and/or mixtures thereof.“Acetates” include the glycol ether acetates.

In certain embodiments, the coatings of the present invention maycomprise from 1 to 100 weight %, such as from 5 to 80 weight %, or from10 to 60 weight % of the polyester polymers described herein based onthe total weight of the coating composition.

In certain embodiments, the coatings of the present invention comprisefrom 0 to 80 weight %, such as from 5 to 60 weight %, or from 8 to 40weight % of a crosslinker or combination of crosslinkers based on thetotal weight of the coating composition.

It will be appreciated that the polyester polymers of the presentinvention (and crosslinkers if used) can form all or part of thefilm-forming resin of the coating. In certain embodiments, one or moreadditional film-forming resins are also used in the coating. Forexample, the coating compositions can comprise any of a variety ofthermoplastic and/or thermosetting compositions known in the art.

Thermosetting or curable coating compositions typically comprisefilm-forming polymers or resins having functional groups that arereactive with either themselves or a crosslinking agent. The additionalfilm-forming resin can be selected from, for example, acrylic polymers,additional polyester polymers that are the same or different than thosedescribed above, polyurethane polymers, polyamide polymers, polyetherpolymers, polysiloxane polymers, polyepoxy polymers, epoxy resins, vinylresins, copolymers thereof, and mixtures thereof. Generally, thesepolymers can be any polymers of these types made by any method known tothose skilled in the art. The functional groups on the film-formingresin may be selected from any of a variety of reactive functionalgroups including, for example, carboxylic acid groups, amine groups,epoxide groups, hydroxyl groups, thiol groups, carbamate groups, amidegroups, urea groups, isocyanate groups (including blocked isocyanategroups) mercaptan groups, and combinations thereof. Appropriate mixturesof film-forming resins may also be used in the preparation of thepresent coating compositions.

Thermosetting coating compositions typically comprise a crosslinkingagent that may be selected from any of the crosslinkers described aboveor known in the art to react with the functionality used in the coating.In certain embodiments, the present coatings comprise a thermosettingfilm-forming polymer or resin and a crosslinking agent therefor and thecrosslinker is either the same or different from the crosslinker that isused to crosslink the polyesters described herein. In certain otherembodiments, a thermosetting film-forming polymer or resin havingfunctional groups that are reactive with themselves are used; in thismanner, such thermosetting coatings are self-crosslinking.

In certain embodiments, the coatings of the present invention alsoinclude a curing catalyst. Any curing catalyst typically used tocatalyze crosslinking reactions between polyester resins andcrosslinkers may be used, and there are no particular limitations on thecatalyst. Non-limiting examples of such a curing catalyst includephosphoric acid, alkyl aryl sulphonic acid, dodecyl benzene sulphonicacid, dinonyl naphthalene sulphonic acid, and dinonyl naphthalenedisulphonic acid; complexes of organometallic compounds including tin,zinc, or bismuth; or tertiary amine bases. “Curing” refers to bondformation between the polyester and crosslinker resulting in theformation of a crosslinked coating. Curing may occur upon application ofan external stimulus including, but not limited to, heat, ultravioletirradiation, exposure to moisture, and exposure to atmospheric oxygen.

In certain embodiments, the coatings of the present invention maycomprise from 0 to 7 weight %, such as from 0.001 to 5 weight % of acuring catalyst based on the total weight of the coating composition.

The coating compositions of the present invention can also include otheroptional materials well known in the art of formulating coatings. Forexample, the coating compositions of the present invention can alsoinclude a colorant. As used herein, “colorant” refers to any substancethat imparts color and/or other opacity and/or other visual effect tothe composition. The colorant can be added to the coating in anysuitable form, such as discrete particles, dispersions, solutions and/orflakes. A single colorant or a mixture of two or more colorants can beused in the coatings of the present invention. A “filler,” on the otherhand, does not necessarily impart any color and/or opacity and/or othervisual effect to the composition.

Examples of colorants include pigments (organic or inorganic), dyes andtints, such as those used in the paint industry and/or listed in the DryColor Manufacturers Association (DCMA), as well as special effectcompositions. A colorant may include, for example, a finely dividedsolid powder that is insoluble but wettable under the conditions of use.A colorant can be organic or inorganic and can be agglomerated ornon-agglomerated. Colorants can be incorporated into the coatings by useof a grind vehicle, such as an acrylic grind vehicle, the use of whichwill be familiar to one skilled in the art.

Examples of pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, diazo,naphthol AS, salt type (flakes), benzimidazolone, isoindolinone,isoindoline and polycyclic phthalocyanine, quinacridone, perylene,perinone, diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine,triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole red(“DPPBO red”), titanium dioxide, carbon black and mixtures thereof. Theterms “pigment” and “colored filler” can be used interchangeably.

Examples of dyes include, but are not limited to, those that are solventand/or aqueous based such as phthalo green or blue, iron oxide, bismuthvanadate, anthraquinone, perylene, and quinacridone.

Examples of tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM® 896commercially available from Degussa, Inc., CHARISMA COLORANTS andMAXITONER INDUSTRIAL COLORANTS commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersionincluding, but not limited to, a nanoparticle dispersion. Nanoparticledispersions can include one or more highly dispersed nanoparticlecolorants and/or colorant particles that produce a desired visible colorand/or opacity and/or visual effect. Nanoparticle dispersions caninclude colorants such as pigments or dyes having a particle size ofless than 150 nm, such as less than 70 nm, or less than 30 nm.Nanoparticles can be produced by milling stock organic or inorganicpigments with grinding media having a particle size of less than 0.5 mm.Examples of nanoparticle dispersions and methods for making them areidentified in U.S. Pat. No. 6,875,800 B2, which is incorporated hereinby reference. Nanoparticle dispersions can also be produced bycrystallization, precipitation, gas phase condensation, and chemicalattrition (i.e., partial dissolution).

In order to minimize re-agglomeration of nanoparticles within thecomposition and resulting coating, a dispersion of resin-coatednanoparticles can sometimes be used. As used herein, a “dispersion ofresin-coated nanoparticles” refers to a continuous phase in which isdispersed discreet “composite microparticles” that comprise ananoparticle and a resin coating on the nanoparticle. Examples ofdispersions of resin-coated nanoparticles and methods for making themare described, for example, in U.S. Pat. No. 7,605,194 at col. 3, line56 to col. 16, line 25, the cited portion of which is incorporatedherein by reference.

Examples of special effect compositions that may be used in thecompositions of the present invention include pigments and/orcompositions that produce one or more visual effects such asreflectance, pearlescence, metallic sheen, phosphorescence,fluorescence, photochromism, photosensitivity, thermochromism,goniochromism, and/or color-change. Additional special effectcompositions can provide other perceptible properties, such as opacityor texture. In a non-limiting embodiment, special effect compositionscan produce a color shift, such that the color of the coating changeswhen the coating is viewed at different angles. Example color effectcompositions are identified in U.S. Pat. No. 6,894,086, incorporatedherein by reference. Additional color effect compositions can includetransparent coated mica and/or synthetic mica, coated silica, coatedalumina, a transparent liquid crystal pigment, a liquid crystal coating,and/or any composition wherein interference results from a refractiveindex differential within the material and not because of the refractiveindex differential between the surface of the material and the air.

Other non-limiting examples of materials that can be used with thecoating compositions of the present invention include plasticizers,abrasion resistant particles, corrosion resistant particles, corrosioninhibiting additives, fillers including, but not limited to, micas,talc, clays, and inorganic minerals, anti-oxidants, hindered amine lightstabilizers, UV light absorbers and stabilizers, surfactants, flow andsurface control agents, thixotropic agents, fillers, organic cosolvents,reactive diluents, catalysts, reaction inhibitors, and other customaryauxiliaries.

In certain embodiments, the optional materials such as colorants maycomprise from 0 weight % to 80 weight %, such as from 0.01 weight % to60 weight % based on total weight of the coating composition.

The coatings of the present invention can be applied to a wide range ofsubstrates known in the coatings industry. For example, the coatings ofthe present invention can be applied to automotive substrates,industrial substrates, packaging substrates, wood flooring andfurniture, apparel, electronics, including housings and circuit boards,glass and transparencies, sports equipment, including golf balls, andthe like. These substrates can be, for example, metallic ornon-metallic. Metallic substrates include tin, steel, tin-plated steel,chromium passivated steel, galvanized steel, aluminum, and/or aluminumfoil. Non-metallic substrates include polymeric, plastic, polyester,polyolefin, polyamide, cellulosic, polystyrene, polyacrylic,poly(ethylene naphthalate), polypropylene, polyethylene, nylon, EVOH,polylactic acid, other “green” polymeric substrates,poly(ethyleneterephthalate) (PET), polycarbonate, polycarbonateacrylobutadiene styrene (PC/ABS), polyamide, wood, veneer, woodcomposite, particle board, medium density fiberboard, cement, stone,glass, paper, cardboard, textiles, or leather (both synthetic andnatural), and the like.

The coatings of the present invention can be applied by any meansstandard in the art, such as electrocoating, spraying, electrostaticspraying, dipping, rolling, brushing, and the like. The coatings of thepresent invention can be applied to a dry film thickness of 0.05 mils to20 mils, such as from 0.5 mils to 5 mils, or from 0.8 mils to 3 mils.

The polyesters described above can be used in a variety of coatingtypes. For example, the polyesters can be used with a one component(1K), or multi-component compositions, such as two component (2K) ormore. As used herein, a 1K coating composition refers to a compositionwherein all the coating components are maintained in the same containerafter manufacture, during storage, etc. In a 1K coating, the reactivecomponents do not readily react at ambient or slightly thermalconditions, but instead only react upon activation by an external energysource. As used herein, “ambient conditions” refers to room temperatureand humidity conditions or temperature and humidity conditions that aretypically found in the area in which the coating composition is beingapplied to a substrate, while “slightly thermal conditions” aretemperatures that are slightly above ambient temperature but aregenerally below the curing temperature for the coating composition. A 1Kcoating can be applied to a substrate and cured by any conventionalmeans, such as by heating, forced air, and the like. In contrast, amulti-component composition such as a 2K composition refers to a coatingin which various components are maintained separately until just priorto application. In a multi-component composition, the reactivecomponents readily react and cure without activation from an externalenergy source.

The coating compositions of the present invention may be used asclearcoats or pigmented coats. A clearcoat refers to a coating that issubstantially transparent. A clearcoat can, therefore, have some degreeof color, provided it does not make the clearcoat opaque or otherwiseaffect, to any significant degree, the ability to see the underlyingsubstrate. In contrast, a pigmented coat will impart some sort of colorand/or other visual effect to the substrate to which it is applied.

The coating compositions of the present invention may also be used aloneor in combination as primers, basecoats, and/or topcoats. A “primercoating composition” refers to coating compositions from which anundercoating may be deposited onto a substrate in order to prepare thesurface for application of a protective or decorative coating system.Such compositions are often topcoated with a protective and decorativecoating system, such as a monocoat topcoat or a combination of apigmented base coating composition and a clearcoat composition.

It has been found that coating compositions including polyester polymershaving lignin in the backbone thereof are less costly than traditionalpolyester polymers not including lignin in the backbone thereof andprovide corrosion resistance to substrates. In addition, the coatingcomposition of the present invention provides increased protection of anunderlying substrate, such as a metallic substrate (e.g. a steelsubstrate) from corrosion as compared to a substrate coated with acoating composition comprising a polyester polymer not incorporatinglignin. As such, the present invention further includes a method ofprotecting a substrate from corrosion comprising applying to thesubstrate the polyester coating composition incorporating lignin asdescribed herein.

The following examples are presented to demonstrate the generalprinciples of the invention. The invention should not be considered aslimited to the specific examples presented. All parts and percentages inthe examples are by weight unless otherwise indicated.

EXAMPLES Example 1 Polyester Polymers for Clearcoats

Polyester polymers for use in clearcoat compositions were prepared usingthe components listed in Table 1. In each of Examples 1A, 1B, 1C, and1D, all components except solvent were combined and heated under anitrogen atmosphere to 220° C. and held for the time indicated inTable 1. The reaction products had acid values (mg KOH/g) as indicatedin Table 1. The samples were cooled to ambient temperature and dissolvedin solvent as indicated in Table 1.

TABLE 1 Components (weight in grams) Ex. 1D Ex. 1A Ex. 1B Ex. 1C 10%Control 10% lignin 20% lignin lignin 2-methyl-1,3-propenediol 246.6215.51 197.64 972 trimethylolpropane 8.27 7.22 6.63 32.59 adipic acid59.02 51.57 47.29 232.6 isophthalic acid 191.24 167.09 153.24 753.6phthalic anhydride 170.50 148.96 136.62 671.9 butyl stannoic acid 0.680.65 0.65 2.93 triphenyl phosphate 0.34 0.32 0.32 1.46 PROTOBIND ® 1000¹— 58.68 107.61 264.7 Conditions/Results Reaction time 10 12 14 16 Acidvalue (mgKOH/g) 3.8 9.5 12.0 10.1 Solvent added² 328.1 312.4 141.6 392.0¹Wheat straw lignin supplied by ALM India ²Solvent mixture 63 wt. %1-methoxy-2-propanol, 18.5 wt % butanol, 18.5 wt % SOLVESSO 100 (napthasolvent supplied by Exxon Mobil Chemical.)

Example 2 Clearcoats

Clearcoat compositions were prepared from the polyester polymers ofExample 1 by combining all solvents in a suitable sized container, andadding the polyester polymers and other components in the order shown inTable 2. The clearcoat compositions were drawn down on aluminumsubstrates to approximately 0.70 mil and baked in a conveyor oven for 30seconds to a peak metal temperature of 450° F. All panels passed 100 MEKrubs (cure) and exhibited 5B crosshatch adhesion (no removal). Pencilhardness and gloss retention showed increases with the increase inlignin content. Flexibility was tested using reverse impact at 30 lbs.All offsets passed reverse impact with no pick and no cracking.

TABLE 2 Ex. 2C (polyester Components Ex. 2A Ex. 2B (polyester with 20%(weight in grams) (control) with 10% lignin) lignin) Polyester Ex. 1A139.67 — — Polyester Ex. 1B — 127.43 — Polyester Ex. 1C — — 128.07hexamethoxymethyl melamine 7.96 16.61 23.27 resin³ butanol 3.00 3.003.00 DIAX ® 2770⁴ 0.40 0.40 0.40 COROC ® A-72-A260⁵ 0.50 0.50 0.50COROC ® A-620-A2⁶ 0.83 0.83 0.83 para-toluene sulfonic acid 0.50 0.500.50 SOLVESSO ® 100 12.50 21.00 26.00 ethylene glycol monobutyl 12.50210.00 26.00 ether ³Supplied by Allnex Belgium SA/NV, Brussels, Belgium⁴Hyberbranched hydrocarbon polymer supplied by Baker Hughes, Houston, TX⁵Acrylic resin supplied by Arkema Coating Resins, Cary, NC ⁶Acrylicresin supplied by Arkema Coating Resins, Cary, NC

Example 3 Primers with lignin polyester

Primer compositions were prepared from polyester polymers of Example 1by combining all solvents in a suitable sized container and adding thepolyester polymer and the other components in the order shown in Table3.

TABLE 3 Wheat No lignin in straw lignin Components primer resin inprimer resin (weight in grams) Ex. 4A Ex. 4B Ex. 4C Ex. 4D Polyester Ex.1A 123.0 123.0 Polyester Ex. ID 90.5 90.5 phosphatized epoxy resin⁷ 8.18.1 8.1 8.1 hexamethoxymethyl 15.0 15.0 36.6 36.6 melamine resin wheatstraw lignin powder — 20.0 — 20.0 (PROTOBIND ® 1000) filler n-butylalcohol — 3.0 — — SOLYESSO ® 100 7.0 24.5 15.5 35.8 2-butoxyethanol 7.024.5 15.5 35.8 toluene sulfonic acid solution 0.5 0.5 0.5 0.5 Total160.6 218.6 166.7 227.3 ⁷Supplied by PPG Industries, Inc.

The topcoated samples were subjected to 2000 hours of salt spray testingto ASTM B117 in which the samples were exposed to a 5% NaCl salt fog atpH 6.2-7.2 at 35° C. (95° F.). Salt spray test results are reported inTable 4.

TABLE 4 Salt Spray after 2000 Hours Scribe Creep Example (mm) PrimerComposition Aluminum 4A 0 Polyester control 4B 0 Polyester resin and 20wt. % wheat straw lignin powder added as filler 4C 0 Polyester/10%lignin resin 4D 0 Polyester/10% lignin resin and 20 wt. % wheat strawlignin powder HDG 4A 15.9 Polyester control 4B 5.9 Polyester resin and20 wt. % wheat straw lignin powder added as filler 4C 8.7 Polyester/10%lignin resin 4D 5.6 Polyester/10% lignin resin and 20 wt. % wheat strawlignin powder

Examples 4C and 4D (10% lignin, without and with lignin filler,respectively) exhibited improved corrosion resistance over Examples 4Aand 4B (no lignin, without and with lignin filler, respectively).

Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details should be regarded as limitations upon the scope of theinvention except insofar as they are included in the accompanyingclaims.

The invention claimed is:
 1. A thermoset coating composition comprisinga polyester prepared from a reaction mixture comprising (a) apolycarboxylic acid component and (b) a polyol component comprisinglignin, such that residues of lignin are incorporated into thepolyester.
 2. The coating composition of claim 1, wherein said polyolcomponent further comprises a hydroxyl functional component other thanlignin.
 3. The coating composition of claim 2, wherein the weight ratioof the lignin to the hydroxyl functional component is 1:30 to 30:1. 4.The coating composition of claim 2, wherein lignin comprises 1 to 50weight % of the polyester, with the weight % based on total solids. 5.The coating composition of claim 1, wherein the lignin comprises wheatstraw lignin.
 6. The coating composition of claim 1, wherein the lignincomprises wood lignin.
 7. A coating system comprising a primer coatingand at least one coating layer thereover, the primer coating comprisingthe coating composition of claim
 1. 8. The coating system of claim 7,wherein said at least one coating layer comprises a colored pigment. 9.The coating system of claim 7, wherein said at least one coating layercomprises a clearcoat layer.
 10. A substrate coated at least in partwith the coating composition of claim
 1. 11. The substrate of claim 10,wherein the substrate is metallic.
 12. The substrate of claim 11,wherein the coating composition provides increased protection of themetallic substrate from corrosion as compared to a substrate coated witha coating composition comprising a polyester polymer not incorporatinglignin.
 13. The substrate of claim 10, wherein the substrate is wood orplastic.
 14. A method of protecting a substrate from corrosioncomprising applying to the substrate the coating composition of claim 1.15. The method of claim 14 wherein the substrate is metallic.